Since the first birth control pill regimen was described, attempts have been made to lower the total steroid dosage in the regimen, while maintaining the regimen's reliability in providing contraception.
For example, U.S. Pat. No. 4,628,051 to Ortho Pharm. Corp. discloses a three phase oral contraceptive containing estrogen and progestogen for administration over 21 days having a lower total monthly steroid dose having the same amount of estrogen in each phase. In the first phase, 5 to 8 tablets containing 0.02 to 0.05 milligrams (mg) ethinyl estradiol ("EE") and 0.065 to 0.75 mg of norethindorone ("NE") are administered daily. In the second phase, 7 to 11 tablets containing the same dosage of EE and 0.25 to 1 mg of NE are administered. In the third phase, 3 to 7 tablets containing the same dosage of EE and 0.35 to 2 mg of NE are administered. While an adequate contraceptive regimen, a 7 day pill free interval can lead to follicular development and thus pregnancy. Furthermore the preferred and described regimens administer 0.735 mg of EE, which to some is considered too large a dosage. Similar regimens are described in U.S. Pat. Nos. 4,616,006, 4,544,554, and 4,530,839 also to Ortho Pharm. Corp.
West German patent application no. 3,341,638 to Hesslinger discloses another triphasic contraceptive regimen wherein contraceptive pills are administered over 22 days. The first phase of this regimen contains 6 pills having 30 .mu.g EE and 0.75 mg lynestrenol. The second phase contains 5 pills having 40 .mu.g EE and 1.0 mg lynestrenol. The third phase contains 11 pills having 30 .mu.g EE and 1.5 mg lynestrenol. This results in a total estrogen dose of 710 .mu.g of EE per cycle.
Another attempt to decrease estrogen levels in triphasic contraceptive regimens is described in Belgian patent 823,689 to Schering AG. In this contraceptive regimen of 21 pills, the first phase consists of 4 to 6 pills containing a first dose of estrogen (e.g. 30 .mu.g EE) and a first dose of progestogen (e.g. 50 .mu.g D-norgestrel). The second phase contains 4 to 6 pills containing one to two times the estrogen dose and one to one and a half times the progestogen dose of the first phase. The third phase contains 9 to 11 pills containing the same or a lesser amount of estrogen as the pills of the first phase, and up to three times the amount of progestogen. A very similar regimen is described in DE 3,347,125, also to Schering AG. Again, the 7 day pill free interval can lead to follicular development and thus pregnancy.
Another patent application of Schering AG (DT 2,645,307) describes a 28 day, 3 stage treatment for treating climacteric disorders. A 28 to 32 day steroid regimen, used in establishing cyclicity in human females, is disclosed in U.S. Pat. No. 3,639,600 to Upjohn wherein 2.550 mg of EE is administered over the treatment period.
DT 2,431,704 to Asche CF & Co. AG discloses a triphasic contraceptive where, in the first stage, a low dose of estrogen (e.g. 0.030 mg EE) and a progestogen (e.g. 1.00 mg norethisterone acetate) are administered for 6 to 8 days; in the second stage, a slightly increased (.ltoreq.2-fold) dose of estrogen and slightly increased (.ltoreq.1.5-fold) dose of progestogen are administered for 6 to 8 days; and, in the third stage, an estrogen dose no higher than the second stage, and an increased (.ltoreq.3-fold of the first stage) progestogen dose are administered for 6 to 8 days. At the very least, 630 g of EE is still administered in this particular regimen.
South African patent 8509-892-A to Warner Lambert Co. describes a three or four phase oral contraceptive regimen having a relatively high amount of norethindrone acetate (i.e. from 0.5 to 1.5 mg) and relatively low amount of EE (10 to 50 .mu.g) or other estrogenic substance. The four phase regimen is administered over a 23 to 34 day cycle having an inactive phase.
European Patent application 253,607 to American Home Prods. discloses a mono-phasic contraceptive preparation containing 23 to 25 dosage units having 0.008 to 0.030 mg of EE in combination with 0.025 to 0.100 mg of desogestrel which is administered over 23 to 25, preferably 24, days followed by a 2 to 5 day pill-free period.
Still another attempt to minimize estrogen levels in sequential oral contraceptives is disclosed in Dutch patent application 6911920 to Unisearch Ltd. This patent application describes a pack containing at least 28 pills, 25 to 27 of which are active. Of the active pills, 17 to 20 are estrogen only (e.g. ethinyl estradiol) pills, with the remainder containing both an estrogen and a progestogen. The low estrogen pills contain 0.050 to 0.080 mg of an estrogen, while the high estrogen pills contain 0.07 to 0.08 mg estrogen. The combination pills contain 0.07 to 0.12 mg estrogen and 0.8 to 1.4 mg of progestogen. Even with this minimized estrogen contraceptive, at least 1.610 mg of estrogen are administered, while in the preferred embodiment, 1.950 mg are administered.
European patent application no. 36,229 to Akzo, nv discloses a multiphase combination-type sequential oral contraceptive consisting of 20 to 22 tablets each containing a progestogen and an estrogen. The first phase contains a relatively low dose of progestogen (e.g. less than 50 micrograms of desogestrel), followed by phases containing more progestogen (e.g. 100 .mu.g and 200 .mu.g desogestrel in the second and third phases, repsectively).
A need exists for an effective low dose contraceptive regimen having the benefits of multiphasic administration (e.g. ideal cycle control), while still preventing follicular development during the pill-free interval.